In my copending application, I have described a microballistic printer in which a plurality of projectiles such as balls are fired from a gun which is spaced from a platen. These projectiles are constantly recycled back to the gun after rebounding from the platen. The gun is controlled by a computer so that successive projectiles strike the platen along loci to form characters on paper or other sheet material bearing against the platen. A printing medium such as carbon paper, inked ribbon, or the like, is superimposed over the paper. When a projectile hits the printing medium, it will form a dot on the paper under it. The control is such that a pattern of dots is formed by successive projectiles to trace the desired character upon the paper. If desired, a manifold of alternate sheets of carbon paper and paper may be used so that carbon copies may be achieved. I have discovered that, when the gun is above a horizontal plane extending at right angles to the platen, when the printing pattern involves a motion from top to bottom--that is, downwardly toward the plane--a projectile being fired from the gun might collide with an antecedently fired projectile rebounding from the platen. At high-speed printing, there is only a short distance between balls, so that this danger becomes increased. Stated otherwise, if I form the characters with the gun above the plane and print with succeeding projectiles being fired toward the plane--that is, downwardly--a succeedingly fired projectile will cross the path of an antecedently fired projectile rebounding from the platen and thus incur the risk of collision. If, however, I form the characters by firing succeeding projectiles away from the plane, an antecedently fired projectile will rebound harmlessly from the platen and a subsequently fired projectile will not cross the path of a previously fired projectile rebounding from the platen. This avoids the danger of collision. Similarly, in respect of forming the characters, if the gun is left of a vertical plane normal to the platen and outside of the printing area, I must print from right to left. If I am printing from a gun positioned to the right of a vertical plane normal to the platen and outside of the printing area, I must print from left to right. This will avoid the danger of collision of a secondly fired projectile with the previously fired projectile rebounding from the platen.